This invention relates to image recording apparatus and, more particularly, it concerns such apparatus which is adapted to record an electronic image generated by a video camera, for example, on a print media scanned by a rotary print head.
The extensive use of card-form media for credit purchasing, licensing and personal identification purposes has led to increased efforts to avoid unauthorized card use and counterfeiting. Early on in the production of identification cards, for example, it was recognized that the provision of various types of visual information on a single card media, such as a photograph, made identification card alteration difficult to accomplish without detection. As a result, highly sophisticated I.D. camera systems are commonly used to combine a colored portrait of the identified person, the identified person's signature and perhaps fingerprints as well as other forms of data in a single photographically produced identification card. Additionally, such equipment had been supplemented with equipment to provide machine readable data on the photographically produced identification cards. The machine readable data is usually recorded on a magnetic strip coated or otherwise mounted on a portion of the card.
More recently, developments in optical or laser printers as well as in the recording media available for use with such printers have provided a capability for recording on a single media card, not only a colored pictorial image of the card holder but also a combination of colored text and machine readable digital code. An identification card read/write system of this type is disclosed in commonly assigned U.S. Pat. No. 4,663,518 issued to Alan Borror et al on May 5, 1987. In this type of system, the pictorial image of the card holder is provided in electronic signal form by a conventional video camera. The video signals are combined with text and data signals in a microprocessor capable of modulating the light source of a laser printer during a single printing operation on the card.
To produce a continuous tone image of the type represented by a colored portrait of a card holder, the laser printer must be capable of traversing a series of closely spaced or adjacent line-form record tracks on the card media in a manner analogous to the presentation of such an image on the CRT of a video receiver. While the existing state of the laser printer art allows a wide latitude of recording track configurations and formats, a combination of high printing speeds and simplicity of required optics is provided by rotary head laser printers of a type disclosed in U.S. Pat. Nos. 4,163,600; 4,219,704; 4,321,700; and 4,426,696. In rotary head printers of this type, optical energy from a single light source is directed to a print media successively through each of a plurality (e.g. five) lenses carried in a continuously rotated wheel. The angular spacing and radial distance of the lenses from the center of wheel rotation is selected in relation to the dimensions of the print media area to be recorded so that with linear movement of the media transverse to the arc traveled by each lens, the requisite series of closely spaced or adjacent record tracks are provided on the media. The combination of arcuate lens travel and linear media feed results in each of the tracks lying on a compound curve.
Although the curved configuration of the record tracks developed by rotary head laser printers is not, in itself, deleterious to the formation of a continuous tone colored image inasmuch as the lines are not visibly discernable without magnification, a problem arises in converting a video image, as read or sensed by a high resolution charge coupled device (CCD) typically used in video cameras, to the curved track configuration of the rotary head laser printer. In particular, video cameras presently use a CCD in the form of a two-dimensional array of sensing elements or pixels aligned in mutually orthogonal striaght lines and columns. Each image sensing pixel converts the incident image defining scene light rays into a corresponding analog voltage value which are thereafter serially transferred out of the CCD to appropriate signal processing circuitry and ultimately as a composite modulated signal to the print head of the printer, in this instance, the light source of the rotary head laser printer. In light of the curved configuration of the printed record tracks as against the straight line configuration of the CCD pixels, the resulting printed image will be distorted in the absence of compensation in the signal processing circuitry. Even if the geometric disparity between the pixel array of the CCD and the printed record was corrected by the signal processing circuitry, some loss of resolution would necessarily result in the printed image.
Accordingly, there is a need for a solution to the problems presented by the use of a converted CCD image with rotary head printers of the general type described.